The present invention relates generally to plasma cutting systems and, more particularly, to a method and apparatus for coordinating the operating modes of a plasma cutter and a portable power supply so that the plasma cutter is prevented from being locked-out when no load is pulled from the power supply.
Many portable power supplies such as generators enter a power saving idle mode when not in use for extended periods of time or when no load is placed thereon. The line voltage and frequency of the power source drop to a level substantially below its rated operation to save fuel, reduce wear, as well as reduce noise, but normally do so only after some period of delay. The power supply then returns to normal operation when a load is placed on its output. Generally, plasma cutters draw significantly less current when idling than when cutting. Further, a plasma cutter in idle mode can operate on a power supply in idle mode, but a plasma cutter in cutting mode cannot operate on a power supply in idle mode.
When a plasma cutter operates on a power supply in idle mode, several undesirable scenarios may occur. For example, the plasma cutter may draw sufficient current to maintain the power supply in normal mode at all times. As a result, the plasma cutter is available at all times but wastes energy and results in unnecessary noise generation by the power supply. Therefore, the efficiency of the plasma cutter and power supply are affected as a result of unnecessary fuel consumption and noise emissions.
In another undesirable scenario, the plasma cutter may not draw enough current to place the power supply back into normal operating mode. As a result, the plasma cutter cannot function properly. If an under-voltage threshold of the plasma cutter prevents the trigger of the plasma cutter from activating, the plasma cutter cannot then draw enough current to kick the power supply out of idle mode. Essentially, the under-voltage threshold detection locks out the plasma cutter when an idle mode of the power supply is detected.
Operation of a plasma cutter on a power supply in idle mode can also result in damage to the plasma cutter as a result of the low frequency of the power supply. In a further wasteful scenario, the operator of the welding system may lock-out the plasma cutter so that the plasma cutter never reaches an idle mode. As a result, the power supply unnecessarily wastes energy and creates noise.
It would therefore be desirable to design a plasma cutting system such that the idle mode of the plasma cutter is coordinated with the idle mode of the power supply such that the plasma cutting system is prevented from being locked-out even when no load is placed on the power supply.
The present invention is directed to a method and apparatus of coordinating the idle mode of a plasma cutter with the idle mode of a power supply overcoming the aforementioned drawbacks. When the power supply is not loaded, the plasma cutter is placed in a sleep mode so as to improve the efficiency of the power supply and plasma cutter as well as reduce unnecessary noise. User input to the plasma cutter such as pressing of a torch trigger switch simulates a load being placed on the power supply and kicks the power supply out of idle. While the plasma cutter cuts, the power supply continues to run in an out-of-idle mode. A control then continuously monitors a trigger mode of the plasma cutter to determine if the plasma cutter is directed toward an idle mode. If so, the control immediately drives the power supply to an idle mode and returns the plasma cutter to a sleep or non-lock-out mode.
In operation, the user of the plasma cutting system plugs the plasma cutter into a power supply and puts the power supply in idle mode followed by turning on the plasma cutter. With most portable power supplies, idle is automatically achieved at initial start-up. The power supply then stays in an idle mode or temporarily goes to a run mode due to an inrush of current from the plasma cutter. The plasma cutter likewise remains in idle mode and waits for a user input, such as activation of a trigger. The plasma cutter may limit its output current during idle and, alternatively, deactivate its boost converter to save power and draw less current. When the user activates the torch activation switch or other activation means, the plasma cutter increases the current draw sufficiently to kick the power supply out of idle mode. After the cut, the plasma cutter current draw drops to a level lower than the power supply idle mode. Once the cut is completed, the plasma cutter may then deactivate the boost converter front end to save power as well as turn off its cooling fan to save power and reactivate an idle mode condition.
Therefore, in accordance with one aspect of the present invention, a controller for a plasma cutting device responsive to a set of instructions that when executed causes the controller to determine an operating state of a power supply is provided. The set of instructions further causes the controller to prevent lock-out of the plasma cutting device even if the power supply is in an idle operating state.
In accordance with another aspect of the present invention, a plasma cutting apparatus includes a plasma cutter and a portable power supply. The plasma cutting apparatus further includes an operating condition coordinator configured to put the plasma cutter in a sleep mode when the portable power supply is not loaded.
In accordance with yet another aspect of the present invention, the plasma cutter apparatus comprises a cable connected to a portable power supply at one end. The apparatus further includes a power source that is configured to condition raw power received from the power supply via the cable. The plasma cutter apparatus further includes a cutting device connected to the power source and means for preventing lock-out of the cutting device if no load is placed on the portable power supply.
Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings.